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  1. 14 Aug, 2017 4 commits
    • Jason Wang's avatar
      tap: XDP support · 761876c8
      Jason Wang authored 
      This patch tries to implement XDP for tun. The implementation was
split into two parts:

- fast path: small and no gso packet. We try to do XDP at page level
  before build_skb(). For XDP_TX, since creating/destroying queues
  were completely under control of userspace, it was implemented
  through generic XDP helper after skb has been built. This could be
  optimized in the future.
- slow path: big or gso packet. We try to do it after skb was created
  through generic XDP helpers.

Test were done through pktgen with small packets.

xdp1 test shows ~41.1% improvement:

Before: ~1.7Mpps
After:  ~2.3Mpps

xdp_redirect to ixgbe shows ~60% improvement:

Before: ~0.8Mpps
After:  ~1.38Mpps
Suggested-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      761876c8
    • Jason Wang's avatar
      net: export some generic xdp helpers · 7c497478
      Jason Wang authored 
      This patch tries to export some generic xdp helpers to drivers. This
can let driver to do XDP for a specific skb. This is useful for the
case when the packet is hard to be processed at page level directly
(e.g jumbo/GSO frame).

With this patch, there's no need for driver to forbid the XDP set when
configuration is not suitable. Instead, it can defer the XDP for
packets that is hard to be processed directly after skb is created.
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      7c497478
    • Jason Wang's avatar
      tap: use build_skb() for small packet · 66ccbc9c
      Jason Wang authored 
      We use tun_alloc_skb() which calls sock_alloc_send_pskb() to allocate
skb in the past. This socket based method is not suitable for high
speed userspace like virtualization which usually:

- ignore sk_sndbuf (INT_MAX) and expect to receive the packet as fast as
  possible
- don't want to be block at sendmsg()

To eliminate the above overheads, this patch tries to use build_skb()
for small packet. We will do this only when the following conditions
are all met:

- TAP instead of TUN
- sk_sndbuf is INT_MAX
- caller don't want to be blocked
- zerocopy is not used
- packet size is smaller enough to use build_skb()

Pktgen from guest to host shows ~11% improvement for rx pps of tap:

Before: ~1.70Mpps
After : ~1.88Mpps

What's more important, this makes it possible to implement XDP for tap
before creating skbs.
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      66ccbc9c
    • Jakub Sitnicki's avatar
      rtnelink: Move link dump consistency check out of the loop · d0225784
      Jakub Sitnicki authored 
      Calls to rtnl_dump_ifinfo() are protected by RTNL lock. So are the
{list,unlist}_netdevice() calls where we bump the net->dev_base_seq
number.

For this reason net->dev_base_seq can't change under out feet while
we're looping over links in rtnl_dump_ifinfo(). So move the check for
net->dev_base_seq change (since the last time we were called) out of the
loop.

This way we avoid giving a wrong impression that there are concurrent
updates to the link list going on while we're iterating over them.
Signed-off-by: default avatarJakub Sitnicki <jkbs@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      d0225784
  3. 11 Aug, 2017 36 commits
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